In LTE (Long Term Evolution), two duplex modes, a frequency division duplex (FDD) mode and a time division duplex (TDD) mode, are defined. In the FDD mode, uplink communication and downlink communication are performed in mutually different frequency bands, and in the TDD mode, uplink communication and downlink communication use an identical frequency band where the uplink communication and the downlink communication are separated in time. In the TDD mode, a ratio of time assigned for uplink/downlink is not limited to 1:1, and different ratios can be applied. Switching between the duplex modes can be performed in inter-frequency handover.
Meanwhile, intra-base station carrier aggregation (intra-eNB CA) has been supported since LTE specification Rel-10. In the carrier aggregation, throughput can be improved by using a bundle of multiple component carriers (CCs).
See 3GPP TSG RAN meeting #61 RP-131399 in detail, for example.